1. Field of the Invention
The present invention relates generally to determining the rate of performing periodic automatic self-tests in such a device.
2. Related Art
Electrotherapy devices are used to provide electrical shocks to treat patients for a variety of heart arrhythmias. For example, external defibrillators typically provide relatively high-energy shocks to a patient as compared to implantable defibrillators, usually through electrodes attached to the patient's torso. External defibrillators are used to convert ventricular fibrillation or shockable tachycardia to a normal sinus rhythm. Similarly, external cardioverters can be used to provide shocks to convert atrial fibrillation to a more normal heart rhythm.
Conventional external defibrillators have been used primarily in hospitals and other medical care facilities. In such environments, the frequency with which a particular defibrillator is operated, referred to as the use model, is significant, perhaps on the order of several times per week. Periodic tests for such defibrillators typically include a battery level test and a functional test in which the defibrillator is connected to a test load and discharged. These self-tests are usually performed daily or once per shift in accordance with manufacturer recommendations. Other tests, such as recalibration of internal circuit components by a biomedical technician, are performed less often, on the order of twice per year, which is also typically specified by the manufacturer. Each of these maintenance tests for conventional defibrillators have traditionally been initiated and performed by human operators, although more recently automatic invocation and execution of self-tests are becoming more commonplace.
While these external defibrillators have been known for years, they have generally been large and expensive making them unsuitable for use outside of a medical care facility. More recently, portable external defibrillators for use by first responders have been developed. Portable defibrillators allow medical care to be provided to a patient at the patient's location considerably earlier than preceding defibrillators, increasing the likelihood of survival.
Portable defibrillators typically use a portable energy source to operate in the anticipated mobile environment. Several defibrillator and after-market manufacturers have produced battery packs for such defibrillators. These battery packs, while often having a standard mechanical and electrical interface, are available with different chemistries, such as lead acid, nickel cadmium, lithium ion and the like. These battery packs have traditionally been rechargeable due to the anticipated high frequency use model.
With recent advances in technology, portable defibrillators have become more automated, allowing even a minimally trained operator to use such devices to aid a heart attack victim in the critical first few minutes subsequent to the onset of sudden cardiac arrest. Such portable defibrillators, referred to as automatic or semi-automatic external defibrillators (generally, AED's), may be stored in an accessible location at a business, home, aircraft or the like. Due to the increased diligence required to properly maintain rechargeable battery packs, some recently developed portable defibrillators have been configured to receive a non-rechargeable battery pack. This is more common in recent history due to advances in battery technology that have allowed for the development of long life, high capacity non-rechargeable battery packs.
One particular problem that arises using currently available portable defibrillators is that occasionally it may be necessary or desired to operate the device in accordance with a use model different than that for which the defibrillator was originally designed. One characteristic of traditional defibrillators that prevents such a change in operation is the implementation of a self-test protocol that verifies the reliability of the defibrillator, including the installed battery pack. The self-test protocol is traditionally established when the defibrillator is manufactured in anticipation that the defibrillator will be used with a particular battery pack. Unfortunately, the defibrillator is required to thereafter restrict the battery packs that it is receives to only the particular type of battery pack that can support and be verified by the implemented self-test protocol. This in turn prevents the defibrillator from being operated in accordance with a use model other than that which the defibrillator was originally designed due to limitations associated with the acceptable type of battery pack.
What is needed, therefore, is a method and apparatus for insuring the reliability and availability of a device such as a portable defibrillator without restricting or otherwise limiting the use model of the device.